Amphiphillic lubricants for magnetic media

ABSTRACT

A magnetic recording medium including a lubricant topcoat having increased bonding to the medium surface comprises an amphiphilic lubricant molecule having a hydrophilic central portion including a plurality of polar functional groups bound to the medium surface and a pair hydrophobic fluoroalkyl ether or perfluoroalkylether end portions at respective ends of the hydrophilic central portion and extending away from the medium surface.

CROSS-REFERENCE TO PROVISIONAL APPLICATIONS

This application claims priority from provisional patent applicationSer. Nos. 60/101,348 and 60/101,356, each filed Sep. 22, 1998, theentire disclosures of which are herein incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to the recording, storage and reading ofmagnetic data, particularly rotatable magnetic recording media, such asthin film magnetic disks having textured surfaces and a lubricanttopcoat for contact with cooperating magnetic transducer heads.

BACKGROUND OF THE INVENTION

Thin film magnetic recording disks and disk drives are conventionallyemployed for storing large amounts of data in magnetizable form. Inoperation, a typical contact start/stop (CSS) method commences when adata transducing head begins to slide against the surface of the disk asthe disk begins to rotate. Upon reaching a predetermined high rotationalspeed, the head floats in air at a predetermined distance from thesurface of the disk, where it is maintained during reading and recordingoperations. Upon terminating operation of the disk drive, the head againbegins to slide against the surface of the disk and eventually stops incontact with and pressing against the disk. Each time the head and diskassembly is driven, the sliding surface of the head repeats the cyclicoperation consisting of stopping, sliding against the surface of thedisk, floating in the air, sliding against the surface of the disk, andstopping.

For optimum consistency and predictability, it is necessary to maintaineach transducer head as close to its associated recording surface aspossible, i.e., to minimize the flying height of the head. Accordingly,a smooth recording surface is preferred, as well as a smooth opposingsurface of the associated transducer head. However, if the head surfaceand the recording surface are too flat, the precision match of thesesurfaces gives rise to excessive stiction and friction during the startup and stopping phases, thereby causing wear to the head and recordingsurfaces, eventually leading to what is referred to as a “head crash.”Thus, there are competing goals of reduced head/disk friction andminimum transducer flying height.

Conventional practices for addressing these apparent competingobjectives involve providing a magnetic disk with a roughened recordingsurface to reduce the head/disk friction by techniques generallyreferred to as “texturing.” Conventional texturing techniques involvemechanical polishing or laser texturing the surface of a disk substrateto provide a texture thereon prior to subsequent deposition of layers,such as an underlayer, a magnetic layer, a protective overcoat, and alubricant topcoat, wherein the texture on the surface of the substrateis intended to be substantially replicated in the subsequently depositedlayers.

A typical longitudinal recording medium is depicted in FIG. 1 andcomprises a non-magnetic substrate 10, typically an aluminum (Al)-alloy,such as an aluminum-magnesium (Al—Mg)-alloy, plated with a layer ofamorphous nickel-phosphorus (NiP). Alternative substrates include glass,glass-ceramic materials, and graphite. Substrate 10 typically includes,sequentially deposited on each side thereof, a chromium (Cr) or aCr-based alloy underlayer 11, 11′, a cobalt (Co)-based alloy magneticlayer 12, 12′, a protective overcoat 13, 13′, typically containingcarbon (C), and a lubricant topcoat 14, 14′. Cr underlayer 11, 11′ canbe applied as a composite comprising a plurality of sub-underlayers 11A,11A′. Cr underlayer 11, 11′, Co-based alloy magnetic layer 12, 12′ andprotective overcoat 13, 13′, typically containing carbon, are usuallydeposited by sputtering techniques performed in an apparatus containingsequential deposition chambers. A conventional Al-alloy substrate isprovided with a NiP plating, primarily to increase the hardness of theAl substrate, serving as a suitable surface to provide a texture, whichis substantially reproduced on the disk surface.

In accordance with conventional practices, a lubricant topcoat isuniformly applied over the protective layer to prevent wear between thedisk and head interface during drive operation. Excessive wear of theprotective overcoat, typically comprising carbon, increases frictionbetween the head and disk, thereby causing catastrophic drive failure.Excess lubricant at the head-disk interface causes high stiction betweenthe head and disk. If stiction is excessive, the drive cannot start andcatastrophic failure occurs. Accordingly, the lubricant thickness mustbe optimized for stiction and friction.

Liquid lubrication of the disk surface has at least two problems whichlimit its effectiveness as used in rotating storage media. First, thelubricant does not have a retention means so that when the disk rotates,the lubricant spins off the disk. The depletion of the lubricantthickness from the disk surface increases the friction between the diskand the read/write head. Second, the depletion of the thickness of thelubricant is not uniform across the surface of the disk. Where thethickness is too thin, the head can cause wear on the disk surface.Where the lubricant thickness is too great, the head will become stuckin the lubricant (from static friction) and the head or disk could bedamaged when the head suddenly becomes unstuck due to the rotating disk.Other failure modes include the inability of the spindle motor to startat all due to the static friction and failure of the mechanicalsuspension assembly. These effects are present even though the depletionis radial in nature.

A significant factor in the performance of a lubricant topcoat is theamount of lubricant which tightly adheres to the magnetic medium, as bychemical bonding forces operating between functional groups of thelubricant molecule and the surface of the recording medium. Typicalconventional lubricants, such as perfluoroalkylpolyether (PFPE) fluidssuch as Fomblin Z-DOL, Fomblin Tx., and Fomblin Z-Tetraol, etc.,generally are comprised of molecules having 2-4 polar groups at eitherend of a linear molecule. The polar end-groups provide bonding of thelubricant molecules to the surface of the magnetic medium. However,polar end-functional groups are not necessarily chemically inert andconsequently, such conventional lubricants may disadvantageously undergochemical reactions prior to their application to the magnetic mediumtending to decrease their bonding potential. Moreover, the conventionalperfluoroalkylpolyether-based lubricants do not have an optimalmolecular structure or conformation considered necessary for theincreased demands of magnetic medium lubricity.

One way in which to increase bonding of the lubricant to the disksurface and therefore prevent the depletion of lubricant therefrom hasbeen to thermally bond the lubricant to the disk surface. However, thistechnique disadvantageously increases the exposure of the magnetic mediato corrosion and degrades the reliability of the disk. Another techniqueis to use a process employing exposure to high energy electron beams.The lubricant is exposed to electron beams having an energy above tenKeV. This process has been shown to produce a modified lubricant filmbonded to the disk surface. However, the modified film does not containall the required lubricating properties of the unmodified film.

Thus, a significant factor in the performance of recording media is thequality and character of the topcoat lubricant. Lubricant topcoatscomprised of conventional polymeric materials as described above aretypically applied as a heterogeneous mixture of different molecularweight species. The use of such mixtures, however, results in dispersalor variation of the properties thereof, depending upon the relativeamounts of each molecular weight fraction present in the mixture. As aconsequence, use of polymer mixtures incurs difficulties in maintaininguniform processing conditions and product quality.

It is also desirable for improved media performance to employ lubricantswhich form an effective functional topcoat at a thickness less thanthose of conventionally utilized lubricants. As indicated above,perfluoropolyether lubricants with one or more functionalized end-groupsare conventionally employed for recording media topcoats. Thefunctionalized end-groups of these compounds are considered necessary toprovide direct bonding, and thus, improved adhesion of the lubricanttopcoat to the recording media. It is also believed, however, that forfunctionalized perfluoropolyether lubricants to provide the requisitetribology, they must be applied at a relatively high topcoat thickness,particularly when the recording medium is expected to perform under highstress conditions.

Perfluoropolyether lubricants with nonfunctionalized end-groups are alsoknown. However, such lubricants have not found significant use as disklubricants since they typically suffer from poor wear resistance.Moreover, commercially available terminally nonfunctionalperfluoropolyether lubricants typically have wide and varyingdistributions of molecular weight components.

In view of the criticality of the lubricant topcoat, there is acontinuing need for improved bonding of the lubricant to the magneticrecording medium, particularly to a carbon-based protective overcoat.There also exists a need for a lubricant topcoat providing improvedstiction and wear performance, particularly under conditions of highstress, temperature, and humidity. There is also a need for lubricantswhich form functionally effective topcoats on recording media at athickness less than conventional lubricant topcoats.

SUMMARY OF THE INVENTION

An advantage of the present invention are improved lubricants suitablefor use as topcoats for magnetic recording media, wherein the lubricantscomprise amphiphilic molecules having a central polyfunctional polargroup moiety and a pair of fluoroalkyl ether end groups at respectiveends of the central moiety.

Another advantage of the present invention is a magnetic recordingmedium comprising a lubricant topcoat thereon exhibiting good stictionand wear resistance, wherein the lubricant topcoat comprises anamphiphilic lubricant molecule.

Yet another advantage of the present invention is a method ofmanufacturing a magnetic recording medium having a lubricant topcoatcomprising an amphiphilic lubricant molecule.

A still further advantage of the present invention is a method of makinga symmetrically configured, amphiphilic lubricant.

Additional advantages and other features of the invention will be setforth in part in the description which follows and in part will becomeapparent to those having ordinary skill in the art upon examination ofthe following or may be learned from the practice of the invention. Theobjects and advantages of the invention may be realized and obtained asparticularly pointed out in the appended claims.

According to the present invention, the foregoing and other advantagesare achieved in part by a substrate having a surface; and a lubricanttopcoat on said substrate surface, wherein the lubricant topcoatcomprises an amphiphilic lubricant molecule having a hydrophilic centralportion including a plurality of polar functional groups and a pair ofhydrophobic fluoroalkylether or perfluoroalkylether end portions atrespective ends of the hydrophilic central portion.

According to embodiments of the present invention, the hydrophiliccentral portion of the lubricant molecule comprises an ester or amide;the lubricant has a molecular weight distribution of about 1.0;comprises a single molecular weight species; and the lubricant moleculehas the formula:

wherein:

A is alkyl, haloalkyl, alkoxy, haloalkoxy, aryl, or haloaryl;

R¹ and R² are independently C₁₋₁₀ fluoroalkyl, or C₁₋₁₀ perfluoroalkyl;

Z and Z′ are independently nitrogen, or oxygen;

x and y are between about 1 to about 10; and

R³ is alkylene, arylene, halosubstituted alkylene or arylene, or(R—J)_(m)—R′; wherein R and R′ are independently alkylene or arylene, orhalosubstituted alkylene or arylene, J is NH, O, S, S—S, SO₂, C(O), orC(S) and m is 1-4.

According to particular embodiments of the present invention, themagnetic recording medium comprises: a substrate; an underlayer on thesubstrate; a magnetic layer on the underlayer; and the lubricant topcoaton the magnetic layer.

According to another aspect of the present invention, a method ofmanufacturing a magnetic recording medium comprises the sequential stepsof:

(a) depositing a magnetic layer on a substrate;

(b) forming a protective overcoat layer over the magnetic layer; and

(c) depositing a lubricant layer on the protective overcoat layer toform a lubricant topcoat; wherein the lubricant topcoat comprises anamphiphilic lubricant molecule having a hydrophilic central portionincluding a plurality of polar functional groups and a pair ofhydrophobic fluoroalkylether or perfluoroalkylether end portions atrespective ends of the hydrophilic central portion.

According to embodiments of the present invention, step (c) comprisesexposing the surface of the protective overcoat to a vapor comprisingthe lubricant or applying a solution of the lubricant in a solvent tothe surface of the protective overcoat, the solvent being at least oneselected from the group consisting of esters, ketones, alcohols, andfluorinated compounds.

According to particular embodiments of the present invention, thesolvent is at least one selected from the group consisting of ethylacetate, ethanol, and acetone; and the lubricant molecule has theformula:

wherein:

A is alkyl, haloalkyl, alkoxy, haloalkoxy, aryl, or haloaryl;

R¹ and R² are independently C₁₋₁₀ fluoroalkyl, or C₁₋₁₀ perfluoroalkyl;

Z and Z′ are independently nitrogen or oxygen;

x and y are between about 1 to about 10; and

R³ is alkylene, arylene, halosubstituted alkylene or arylene, or(R—J)_(m)—R′; wherein R and R′ are independently alkylene or arylene, orhalosubstituted alkylene or arylene, J is NH, O, S, S—S, SO₂, C(O), orC(S) and m is 1-4.

According to yet another aspect of the present invention, a method ofproducing a symmetrically configured amphiphilic lubricant compoundhaving formula (I)

comprises chemically combining two molecules of a compound of formula(II):

with one molecule of a compound of formula (III)

 H—Z—(R⁴)_(m)—Z′—H

wherein:

A is alkyl, haloalkyl, alkoxy,. haloalkoxy, aryl, or haloaryl;

R¹ and R² are independently C₁₋₁₀ fluoroalkyl, or C₁₋₁₀ perfluoroalkyl;

Z′ and Z are independently nitrogen, or oxygen;

x and y are between about 1 to about 10;

m is 1 to 4; and

R⁴ is alkylene, alkylene-oxy, alkylene-thio, alkylene-dithio,alkylene-sulfonyl, or halosubstitued derivatives thereof.

According to particular embodiments of the present invention, the methodcomprises producing a compound of formula:

Additional advantages of the present invention will become readilyapparent to those having ordinary skill in the art from the followingdetailed description, wherein the embodiments of the invention aredescribed, simply by way of illustration of the best mode contemplatedfor carrying out the invention. As will be realized, the invention iscapable of other and different embodiments, and its several details arecapable of modifications in various obvious respects, all withoutdeparting from the invention. Accordingly, the drawings and descriptionare to be regarded as illustrative in nature, and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of the embodiments of the presentinvention can best be understood when read in conjunction with thefollowing drawings, wherein:

FIG. 1 schematically depicts, in cross-sectional view, a portion of amagnetic recording medium structure to which the present invention isapplicable; and

FIGS. 2 and 3, respectively, schematically illustrate the as-bondedstates and conformations of PFPE lubricant molecules according to theconventional art and symmetrically configured, amphiphilic lubricantmolecules according to the present invention.

DESCRIPTION OF THE INVENTION

The present invention stems from the recognition by the presentinventors that conventionally configured PFPE-type lubricants utilizedas topcoats for magnetic recording media do not have optimal molecularconfigurations and properties conducive for strong bonding to magneticrecording media surfaces, e.g., carbon-based protective overcoats.Adverting to FIG. 2, shown therein is a schematic representation of thebonding state/configuration of a conventional PFPE-based lubricant(e.g., Fomblin Zdol, Ausimont). As is evident therefrom, such typelubricant molecules comprise two OH groups at the opposite ends of along polymer chain or backbone, which polar functional groups areutilized for bonding to the media surface. Such configuration possessesseveral drawbacks, i.e., (1) the polar functional groups are notcompletely inert and may provide insufficient bonding of the lubricantmolecule to the media surface; (2) the polar end-groups tend to be boundto the media surface thereby forcing the polymer chain or backbone in adisorderly configuration above the media surface. Moreover, PFPE-baselubricants typically consist of heterogeneous mixture of differentmolecular weight species, which degrade tribological properties.

Referring now to FIG. 3, shown therein is a schematic representation ofthe bonding state/configuration of amphiphilic lubricant moleculeaccording to the present invention. As employed herein, the term“amphiphilic” denotes a molecule having both a hydrophobic moiety orportion and a polar, hydrophilic moiety or portion. Thus the illustratedlubricant molecule according to the present invention (“LC4”,alternatively 3,6-dioxaoctanebis(perfluoro-2,5,8,11-tetramethyl-3,6,9,12-tetraoxapentadecanoyl amideor perfluorinated tetramethyl alkyl ether diamide), comprises ahydrophilic central portion A of length sufficient to extend parallel toand over a portion of the media surface and includes a substantialplurality of polar functional groups or atoms, illustratively nitrogenand oxygen atoms or groups containing same, for bonding therewith in amonolayer thickness, as by dipole-dipole interaction (as indicated byshort solid lines in the figure). A pair of hydrophobic end portions Bextend from respective ends A′, A″ of the hydrophilic central portion Ain the direction away from the media surface, thereby providing auniform monolayer thickness of lubricant directly bonded to the surfaceof the magnetic medium.

The inventive lubricants are designed and synthesized to have anaccurately defined chemical formula or structure and a single molecularweight species, whereby the physical properties thereof are notinfluenced by molecular weight distribution. As a consequence of thedefined structure and single molecular weight, the inventive lubricantsare thus readily adaptable for coating on media surfaces by a vapor lubeprocess, without fractionation.

The inventive lubricant molecules can be represented by the followingformula:

wherein:

A is alkyl, haloalkyl, alkoxy, haloalkoxy, aryl, or haloaryl;

R¹ and R² are independently C₁₋₁₀ fluoroalkyl, or C₁₋₁₀ perfluoroalkyl;

Z and Z′ are independently nitrogen, or oxygen;

x and y are between about 1 to about 10; and

R³ is alkylene, arylene, halosubstituted alkylene or arylene, or(R—J)_(m)—R′; wherein R and R′ are independently alkylene or arylene, orhalosubstituted alkylene or arylene, J is NH, O, S, S—S, SO₂, C(O), orC(S) and m is 1-4.

Thus, the present invention is directed to a class of lubricants whichcan be advantageously employed as lubricant topcoats on magneticrecording media with an increased degree of direct bonding to themagnetic media vis-à-vis conventional PFPE-based lubricants, especiallywhen applied to a protective overcoat. The lubricants of the presentinvention can be bonded in a controlled manner to various protectiveovercoat materials, including, e.g., carbon, silicon dioxide,hydrogenated carbon, nitrogenated carbon, and graphitic carbon as ahighly oriented monolayer, thereby advantageously reducing topcoatthickness. A particularly advantageous characteristic of the inventiveclass of lubricants is the ability to tailor their molecularconfiguration to achieve a controlled affinity for a particular topcoatmaterial and surface topography, thereby providing a controlled “bondedlube” ratio and protection against degradation/disbonding resulting frommoisture penetration/absorption, as under exposure to conditions of highhumidity. For example, the chain length of the hydrophobic end portionsB can be easily changed from short to long and from hydrocarbon tofluorocarbon segments, or to a combination of both. Consequently, theinventive class of lubricants can be tailored as to be readily andeffectively applied to various protective topcoat materials with acontrolled bonded lube ratio and attendant reduction in stiction, whileproviding an increase in wear resistance and durability.

In an embodiment of the present invention, the lubricant moleculescomprise stable, single molecular weight (i.e., a molecular weightdistribution of about 1), symmetrically configured, amphiphilicmolecules having a hydrophilic central portion including a plurality ofpolar functional groups for providing bonding to the surface of amagnetic recording media, and a pair of substantially identical,elongated hydrophobic fluoroalkylether or perfluoroalkylether endportions at opposite ends of the hydrophilic central portion adapted forextending in the direction away from the media surface for providingimproved tribology.

Several specific examples of amphiphilic lubricants according to thepresent invention, designated LC-4, LC-5, LC-6, and LC-7, and theirrespective molecular weights, are given in Table 1 below.

TABLE 1 Formula Lubricant Compound Weight

1768.6

1765.2

1768.9

1724.4

In each case, the viscosity of the above-listed lubricants exceeds thatof Fomblin Z Tetraol (Ausimont).

The inventive compounds are conveniently synthesized according to areaction scheme as illustrated below:

wherein:

A is alkyl, haloalkyl, alkoxy, haloalkoxy, aryl, or haloaryl;

R¹ and R² are independently C₁₋₁₀ fluoroalkyl or C₁₋₁₀ perfluoroalkyl;

Z′ and Z are independently nitrogen, oxygen or sulfur;

x and y are between 1 and 10; and

R³ is alkylene, arylene, halosubstituted alkylene or arylene, or(R—J)_(m)—R′; wherein R and R′ are independently alkylene or arylene, orhalosubstituted alkylene or arylene, J is NH, O, S, S—S, SO₂, C(O), orC(S) and m is 1-4.

By way of illustration, but not limitation, the above-illustratedsynthesis can be performed according to the following procedure, whichyields products having a single molecular weight species and an impuritylevel of less than about 0.1%, as determined by chromatographic andother analytical methods:

(1) mix the selected H—Z—R³—Z′—H compound, e.g., a diamine, with asuitable solvent, e.g., pyridine or perfluoropyridine, at roomtemperature to form a solution;

(2) reduce the temperature of the thus-prepared solution to about 0° C.,as by cooling with ice;

(3) add the selected A(R¹O)_(x)(R₂O)_(y)—C(O)—F compound (e.g., aperfluoro ether) to the cooled solution in a molecular ratio slightlygreater than 2:1;

(4) permit the reaction mixture to stand at room temperature for about24 hours;

(5) separate the crude product from the solvent by evaporating thesolvent; and

(6) purify and isolate the desired compound by chromatography.

A variety of fluoro and perfluoro ether compounds for forming thehydrophobic end portions may be utilized for reaction according to theabove process scheme with a variety of diamino compounds for forming thehydrophilic central portions.

In a particular embodiment R³ is (R⁴)_(m) wherein R⁴ is alkylene,alkylene-oxy, alkylene-thio, alkylene-dithio or alkylene-sulfonyl orhalosubstituted derivatives thereof and m is 1-4. By way of example, ageneral synthetic route utilizing perfluoro ether compounds and diaminesto form LC4 and LC_(n) type lubricants and analogs thereof can berepresented as follows:

Examples of diamines which may be utilized in the above reaction schemeinclude:

NH₂CH₂CH₂OCH₂CH₂OCH₂CH₂NH₂ 1,8-diamino-3,6-doxaoctane H₂NCH₂CH₂NH₂ethylene diamine H₂NCH₂CH₂SSCH₂CH₂NH₂ cystamine H₂NCH₂CH₂CH₂NH₂1,3-diaminopropane H₂NCH₂C(O)CH₂NH₂, 2HCl.H₂O 1,3-diaminoacetonedihydro- chloride monohydrate H₂NCH₂CH₂CH₂CH₂NH₂ 1,4-diaminobutaneH₂NCH₂C(O)CH₂CH₂NH₂, 2HCl 1,4-diamino-2-butanone dihydrochlorideH₂NCH₂(CH₂)₆CH₂NH₂ 1,8-diaminooctane H₂NCH₂CH₂OCH₂CH₂NH₂, 2HCl2,2-oxybis (ethylamine) dihydrochloride H₂NCH₂CH₂NHCH₂CH₂NH₂diethylenetriamine (H₂NC₆H₄)₂SO₂ Aminophenylsulfone

Referring again to FIG. 3, the molecular structure of the LC4 and LC_(n)type lubricants each contain a central hydrophilic portion A comprisedof two polar groups, i.e., amide-containing moieties generallyrepresented as —C(O)—NH— and —NH—(O)C—, separated by a chain segment.The amide moieties each contain highly electronegative, and thus highlypolar oxygen (O) and nitrogen (N) atoms, and thus strongly bond thecentral hydrophilic portion A of the LC4 and LC_(n) type lubricantmolecules to the recording media surface (e.g., the protective overcoat)via dipole-dipole interactions at the contact interface. In addition tothe bonding provided by the amide moieties, additional dipole-dipolesurface bonding is provided by the oxygen (O) atoms of each of the etherlinkages. The strong surface bonding of central portion A provided bythe combination of amide moiety and ether linkage results in monolayerthicknesses (i.e., less than about 15 Å) of the lubricant, including ahighly oriented, close-packed arrangement of bonded lubricant moleculeswith their respective symmetrically structured hydrophobic end portionsB extending away from the media surface for providing lubricity andprevention of moisture penetration to the central bonding portion A,thereby reducing degradation of the dipole-dipole bonds. Moreover, thelength of the chain segment between the polar amide bonding moieties canbe easily changed from short to long and from hydrocarbon to fluorinatedhydrocarbon, or a combination of both, by appropriate selection of thediamine reactant. Thus, the LC4 and LC_(n) type lubricants can betailored for optimum use with particular types of carbon-basedprotective overcoats.

The lubricant topcoat of the present invention can be applied to eitherthe magnetic recording layer of the medium or to a conventionallyapplied protective overcoat, particularly a carbon-based overcoat, byexposing the surface receiving the lubricant topcoat to a vaporcomprising the lubricant or by applying thereto a solution of thelubricant in an appropriate solvent, as by dipping thereinto. As for theformer process, the inventive lubricants are advantageous in that,unlike conventional PFPE type lubricating oils, they comprise a verynarrow molecular weight distribution or a single molecular weightspecies which permits greater control over vapor phase coating. As forthe latter process, the inventive lubricants are advantageous in thatthey are soluble not only in conventional fluorinated solvents (e.g.,Vertrel and PF 5060), but are soluble in common, inexpensive solventssuch as ethyl acetate, ethanol, acetone, and mixtures thereof.Consequently, use of the inventive lubricants for dip coating ofmagnetic recording media can reduce cost as well as environmentalpollution.

The present invention is not limited to any particular type of magneticrecording medium, but can be employed in any of various magneticrecording media, including those wherein the substrate or a subsequentlydeposited base layer has been textured, as by mechanical treatment or bylaser techniques, and the textured surface substantially reproduced onsubsequently deposited layers. Thus, a lubricant prepared in accordancewith the present invention, can be applied to form a topcoat, such astopcoat 14 and 14′ on the magnetic recording media depicted in FIG. 1,but is not necessarily limited thereto.

Only the preferred embodiment of the present invention and an example ofits versatility is shown and described in the present disclosure. It isto be understood that the present invention is capable of use in variousother combinations and environments and is capable of changes ormodifications within the scope of the inventive concept as expressedherein.

What is claimed is:
 1. A magnetic recording medium comprising: anon-magnetic substrate; an underlayer on the substrate; a magnetic layeron the underlayer; and a lubricant topcoat on the magnetic layer,wherein the lubricant topcoat comprises a lubricant having a molecularweight distribution of about 1 and having the formula:

 wherein: A is alkyl, haloalkyl, alkoxy, or haloalkoxy; R¹ and R² areindependently C₁₋₁₀ fluoroalkyl, or C₁₋₁₀ perfluoroalkyl; Z and Z′ areNH; x and y are between about 1 to about 10; and R³ is alkylene,halosubstituted alkylene or (R—J)_(m)—R′; wherein R and R′ areindependently alkylene or halosubstituted alkylene, J is NH, O, S, S—S,SO₂, C(O), or C(S) and m is 1-4.
 2. The magnetic recording mediumaccording to claim 1, wherein the lubricant comprises a single molecularweight species.
 3. The magnetic recording medium according to claim 1,further comprising a protective overcoat on the magnetic layer and thelubricant topcoat on the protective overcoat.
 4. The magnetic recordingmedium according to claim 3, wherein the lubricant comprises a singlemolecular weight species.
 5. The magnetic recording medium according toclaim 1, wherein the lubricant molecule has the formula:


6. The magnetic recording medium according to claim 1, wherein thelubricant molecule has the formula:


7. A method of manufacturing a magnetic recording medium, the methodcomprising the sequential steps of: (a) depositing an underlayer on anon magnetic substrate (b) depositing a magnetic layer on saidunderlayer; (c) forming a protective overcoat layer over the magneticlayer; and (d) depositing a lubricant layer on the protective overcoatlayer to form a lubricant topcoat; wherein the lubricant topcoatcomprises a lubricant having a molecular weight distribution of about 1and having the formula:

 wherein: A is alkyl, haloalkyl, alkoxy, or haloalkoxy; R¹ and R² areindependently C₁₋₁₀ fluoroalkyl, or C₁₋₁₀ perfluoroalkyl; Z and Z′ areNH; x and y are between about 1 to about 10; and R³ is alkylene,halosubstituted alkylene or (R—J)_(m)—R′; wherein R and R′ areindependently alkylene or halosubstituted alkylene, J is NH, O, S, S—S,SO₂, C(O), or C(S) and m is 1-4.
 8. The method according to claim 7,wherein: step (b) comprises exposing the surface of the protectiveovercoat to a vapor comprising the lubricant.
 9. The method according toclaim 7, wherein: step (d) comprises applying a solution of thelubricant in a solvent to the surface of the protective overcoat. 10.The method according to claim 9, wherein the solvent is selected fromthe group consisting of esters, ketones, alcohols, and fluorinatedcompounds.
 11. The method according to claim 10, wherein the solvent isselected from the group consisting of ethyl acetate, ethanol, andacetone.
 12. The method according to claim 7, wherein the lubricantmolecule has the formula: